Incident Summary
On 15 January 2015, a Boeing 787-8 (B788) operating in the Warsaw Flight Information Region (FIR EPWW) experienced a loss of separation with another aircraft following a misunderstanding between the flight crew and air traffic control (ATC). The incident occurred during climb and involved no injuries to crew or passengers.
Sequence of Events
The crew of the B788 initially received clearance to climb to flight level (FL) 320. As they approached FL 300, ATC issued a further clearance to FL 380 as part of a continuous climb procedure, which accounted for another aircraft crossing their route at FL 360. Approximately 11 minutes before the potential conflict with the other aircraft, while the B788 was at FL 320, ATC instructed the crew to “EXPEDITE TO CROSS FL 370.” The crew acknowledged the instruction. However, upon reaching FL 348, the crew ceased the climb without advising ATC. At that time, the sector was busy with over 20 aircraft in communication. ATC detected the lack of climb about 4 minutes before the potential conflict and instructed the B788 crew to execute a turn to ensure the required separation.
Investigation Findings
The investigation determined that the incident resulted from a lack of proper communication between the flight crew and ATC. The crew did not inform ATC that the aircraft's performance prevented them from maintaining the expedited climb rate, which constituted a deviation from good aviation practices.
Probable Cause
The stated cause of the incident was a lack of proper communication between the flight crew and ATC.
Safety Actions
The aircraft operator logged the event in its Safety Management System (SMS) database and included it in safety performance indicators monitored under its Safety Management Manual. No safety recommendations were issued by the investigation commission.